1. Field of the Invention
This invention involves an apparatus and method for installing pipe and control line in an earthen borehole. Specifically, this invention involves a spider having components that are adapted for being manipulated to facilitate securing of control line to a pipe string as it is being made up and run into a borehole.
2. Background of the Invention and Related Art
Oil and gas wells may be equipped with control lines for mechanically, electrically, pneumatically, hydraulically or optically linking various downhole devices to the surface. Control lines may be used to receive data from downhole instruments or to operate downhole devices such as valves, switches, sensors, relays or other devices. Control lines may be used to open, close or adjust downhole valves in order to selectively produce or isolate formations at locations deep in the well. A control line may transmit data gathered downhole to the surface or communicate commands to downhole devices to take samples, readings, or to stroke valves. Control lines may comprise electrically conductive wires or cables, optical fibers, or fluid conduits for pneumatically or hydraulically controlling downhole devices or transmitting data.
Control lines are generally of a small diameter relative to the diameter of the pipe string to which they are secured, and are generally between 0.5 and 6 cm in diameter. A plurality of control lines may be aggregated to form an umbilical having a diameter of up to 10 cm or more. Control lines are generally secured along the length of the outer surface of a pipe string, generally parallel to the center axis of the bore of the pipe string. Continuous control lines are secured to the pipe string and installed in the well as joints of pipe are made up into a pipe string and run into a well.
Control lines secured to pipe string are subject to being damaged and being rendered useless if they are pinched or crushed by the pipe slips used to grip and support the pipe string while it is being made up and run into the well. This presents a challenge in securing the control lines to the pipe string as it is made up and run into the borehole. Depending on the diameter, length and pipe thickness, the pipe string may weigh more than four hundred thousand pounds. A pipe-gripping tool called a spider is required to grip and support the pipe string at or near the rig floor. The spider generally comprises a tapered bowl having a bore with an axis that is generally aligned with the borehole. The pipe string passes through the tapered bowl, and the tapered bowl receives a generally circumferential arrangement of radially inwardly movable slips that surround and engage the pipe string within the tapered bowl. The generally wedge-shaped slips are adapted for engaging the outer curved surface of the pipe string and bearing against the tapered inner surface of the bowl to provide generally radially distributed support in a self-tightening manner.
It is important that the pipe slips in the spider generally uniformly grip and support the pipe string in order to minimize localized stress and loads on the pipe that may crush or damage the pipe string. The radially inwardly disposed gripping surfaces of the slips are concave in order to contact the pipe over a radially large area to minimize localized stresses. When control lines are being secured to the pipe and run into the borehole, it is important to prevent the control lines from being pinched or trapped between the spider slips and the outer surface of the pipe string, or between adjacent slips as they move radially inwardly to grip and support the pipe string. If a control line is trapped between the slips and the pipe string or between two adjacent slips, the control line may be damaged with a resulting loss or impairment of surface control of, or communication with, downhole devices or instruments that are linked to other devices or to the surface using control line(s). It is important that control lines be secured to the pipe string in a manner that will prevent control line damage.
One method of installing control lines involves extending the control lines along the portion of the pipe string that is gripped and supported within the tapered bowl of the spider. A control line may be aligned and positioned along the length of the exterior surface of the pipe string to radially coincide with and pass through a gap or recess between adjacent slips. This method may be unsatisfactory where multiple control lines are being secured to the pipe string because more of the circumference of the pipe string is required to accommodate the control lines, leaving less contact circumference for the slips to engage and support the pipe string.
The growing appreciation for the advantages and benefits of controllable downhole tools and devices and for receiving data from downhole instruments has resulted in the development of new tools and methods for installing control lines in a well. One approach involves the use of a table-elevated spider constructed on the rig floor to support the spider and the pipe string, thereby creating and maintaining a clamping zone between the table and the rig floor. This “clamping zone” provides access to a portion of the pipe string beneath the spider for introducing and securing control lines along the length of the pipe string. The control lines are fed to the pipe string at a location underneath the table that supports the spider, secured to the pipe string, and then fed into the borehole along with the pipe string as it is made up and lowered into the borehole. While the table-elevated spider prevents slip damage to control lines at the spider, the legs supporting the table must be strong enough to support the entire pipe string, the spider, and the table, which is a work platform for machines and personnel. The required strength of the legs and the space restrictions of the table present significant expense and safety concerns.
Another approach to securing control lines to a pipe string as it is being made up and run into a well involves a spider adapted for being received in a retainer that can be vertically reciprocated from and to its retracted position within or near the floor of the rig. This invention eliminates the need for an elevated table with legs strong enough to support the spider, table and pipe string. After the weight of the pipe string is transferred to the elevator, the retainer and spider are raised from the floor position to create a temporary clamping zone between the raised spider and the rig floor. The control line may be directed over roller guides or sheaves secured on or adjacent to the retainer that supports the spider so that the control line will conveniently align along the exterior length of the pipe string within the temporary clamping zone. After the central line is secured to the pipe string in the clamping zone, the pipe string and the control line are lowered into the borehole and the retainer and the spider are returned to their original position in or near the rig floor for again receiving and supporting the pipe string while an additional pipe segment is made up into the pipe string.
While vertically reciprocating the spider in this manner eliminates the expense and safety concerns associated with the table-elevated spider, there remains a need to optimize the equipment and the methods for securing control line to a pipe string. What is needed is a method of securing a control line to a pipe string that does not require the repeated movement of the entire spider to establish a clamping zone. What is needed is an apparatus that permits the repeated movement of select components of the spider in order to create a clamping zone for securing control line to the pipe string.